Electromagnetically applied and released brake



March 28, 1961 J D, LEITCH 2,976,963

ELECTROMAGNETICALLY APPLIED AND RELEASED BRAKE Filed April 30, 1957 I 5 Sheets-Sheet 1 March 28, 1961 J, D LEVI-CH 2,976,963

ELECTROMAGNETICALLY APPLIED AND RELEASED 'BRAKE Filed April 50, 1957 5 Sheets-Sheet 2 IGI l I I INVENTOR. JOHN 5/ TCH T 70K/VE KS March 28, 1961 J, D |TCH 2,976,963

ELECTROMAGNETICALLY APPLIED AND RELEASED BRAKE Filed April 50, 1957 3 Sheets-Sheet 5 i/wi lx lf2 f4, if 4;

BY Ml; @Ma- ELECTROMAGNETICALLY APPLIED AND RELEASED BRAKE John D. Leitch, Grosse Pointe Park, Mich., assigner to Square D Company, Detroit, Mich., a corporation of Michigan Filed Apr. so, 1957, ser. No. 656,036 7 claims. (c1. 18s-10s) This inventionrelates to brakes, and more particularly to an industrial brake which is both released and applied n electromagnetically and which is also applied automatically by mechanical means upon disconnection, or accidental failure, of electric power. t

In the operation of many industrial mechanisms, for example, the bridges of electric overhead traveling cranes, it is desirable to control the degree of brake application electrically and yet to have full braking force applied automatically upon failure of power. Heretofore, an electrically operated Vbrake having these capabilities vand also suitable for industrial applications has not been available, and resort has had to lbeV made to hydraulic or pneumatic means for controlling the brake torque or degree of brake application. `Hydraulic and pneumatic brakes have numerous disadvantages, and in their simpler forms cannot be used at all when the structure ontwhich the brake is mounted movesY m'ateriallywith l*respect to the control station.

One of the objects of this invention is to provide an improved industrial brake including electricallyv operated means forvarying its torque electrically.

kAnother object is to provide an improved brake which is held applied by a spring under certain conditions, and which, under other conditions, can-be applied and releasedby the controlofelectromagnetic force ,without interference by the. spring. l 1

Another object is to provide an improved .-electro magnetic operating ,meansV for a spring-.applied vbrake which,-as long as electric powerisl available, isoperable f to nullify the` applyingl force of the Y'spring and con-` currently is operable to apply andrelease the brake and to control the amount of its torque.

Another object 'is to 'provide anV improved industrial brake which isheld applied ,by'aspring whenever electric power is notA available, and-which can be released and applied by control of electric power when poweris availyable without the necessity ofdeactiva`ting the spring during-each release of the brake." A v Prior known all-electric brakes of this general type. have not been suitable `for ,industrial applications, and have'- required the energi'zationof two'c'oils ,to de-activate Lthe spring and subsequent ,deenergiz'atio'n' of-one ofthe coils to release the brake. -A complicated controlfsystem for these prior brakes is necessarybecause of -the required energization` and .subsequent deenergization l;of

one o f the coils. Inthe brake of the present,iin/enticin,`

two. operating vcoils are. provided'in` axcompact'; ,unitary structure. After oneof the coils is energized .to ,coma

2,976,963 Patented YMar. 28, 1961.

ICC

the spring so that it discontinues the kapplication of braking force. In the example herein, the spring is shown as a compression spring and is de-activated by in creasing its compression. The other armature is operative, while the spring is de-activated, to apply the shoes to the wheel with a force related to the amount of current in its associated coil.

Other objects andadvantages of this invention will become apparent from the following description wherein reference is made to the drawings, in which:

Fig. 1 is a side elevation of a brake in accordance with this invention;V

Figs. 2, 3, and 4 are sectional views taken generally as indicated by the lines 2 2, 3-3, and 4--4 in Fig. l, respectively, parts thereof being shown, in each, in ele` vation for clearness of illustration, and

Figs. 5 and 6 are wiring diagrams illustrating exemplary control systems for the brake,

Referring to the general structure of the brake shown in the drawings, the brake comprises a suitable base 10 and inner and outer upstanding shoe levers 11 and 12 carrying brake shoes 14 and' 15, respectively, for cof operation with a brake wheel 16 rotatable with a shaft 18 forming part of a mechanism such as a crane bridge driven by an electric motor (not shown). The outer shoe lever 12 at its lower end portion is pivoted on the base 10 and at its upper end portion is connected to an upper end portion of the vinner shoe lever 1,1 by an ad-v justable tie-rod 19 disposed labove the wheel 16. Thek shoe lever 11 is pivoted intermediate of its ends at upper p end portions of a pair of spaced supports 2t) which are,

in turn, at their lower end portions, pivoted on the base 10. t p l In accordance with this invention, the shoes 14 and 1 5 are normally applied to the wheel 16 by afhelical compresl sion spring 21, disposed withinr the base lil, which urges a lower extension of a generally disc-shaped armature v plate 22 against a thrust rod 24 to force a lower end portion of theV lever 11 to the right as viewed in Fig. l.

The spring 21 is cle-activated, or rendered inoperative,

, upon movement 'of the lower end extension of the armature.22,to the left. The shoes 14 and 15 are also applied to the wheel 16, when the compressiony spring 21 is, inoperative, by force Vexerted by a generallyk discshaped armature plate 25 Lwhich is connected at its lower end portion to theflower end portion of the inner shoe lever 11 by a pairof spaced bars 26 disposed within the base 10 onopposite sides of the spring 21. Y y

The armatureplate 22 is pivoted at its upper end por-y tion Vto an .upper portion of a cylindrical magnet housing Y l Z8 on the. sideof the housing nearest thegbrake wheel 16, and the armature plate 25 is similarly pivoted .atl'its upperv4 end vrportion to an upper portion ofthe housing 2S on theside thereof most remote rfrom the 'brake wheel 16.` i

The magnet .housing 28 has an annularfouterfpole Y 'y portion 29, an axially ,disposed central core .orpole portion 30, and an intermediate radially disposed yannular Web portion 31 defining, within Athe housing 2S, coaxial annular coil-receiving chambers 32 and 33. An annular coil 34 inthe chamber -32 is `arranged to control operation ofthe armature' plate 2,2',` and an .annularcoil35 in press the spring, the other. coil can be energized inselectl.

' of thecoils to Yactivate a brake-applying spring sc ,tht it becmesoperative to apply thebakaaudto deactivate the chamberv 33 is arranged toy control operation of the armaturel plate 2S. l

Referring now toy the structure of the brake in 'greater' l detail,4 the base 10 comprises a pair of spaced side" mem- Y bers 41 interconnected at them'agnet, end by atransverse Y endrportion 42 and in Vthe region under the wheel byfa` relatively wide inverted channel-like portion V44,. Suit.-

able bolt-receiving' Vlugs 45, areprovided at kspaced interi vals along lthe side members '41,.,to, facilitate holding the E brackets 46 extending outwardly from each of the side members 41 receive respective cap screws 47 threaded into respective complementary lugs 43 on the magnet housing 28 thus to secure the housing to the base 10.

The inner shoe lever 11 has upper and lower bifnrcated end portions and 52 which receive respective pins 53 and 54 and, at its central portion, rotatably receives a pin 55. The outer shoe lever 12 is similar and has upper and lower bifuroated portions 56 and 57 which receive pins 53 and 59, respectively, and, at itsl central portieri, rotatably receives a pin 63.

The bifurcated iower end portion 52 of the inner shoe lever 11 rotates on the pin which is secured at its opposite ends to the inner end portions or" the bars 26, respectively, and which rotatably carries intermediate of the bifurcations of the end portion 52 an inner end portion 61 of the'thrust rod 24. The lower end portionr57 of the outer shoe lever 12 rotates on the pin 59 which is secured at its opposite ends to respective side members 41 ofthe base 10.

The pin 53 at the upper end portion 51 of the inner lever 11 is secured at its opposite ends to the respective bifurcations of the lever 11 and rotatably carries between the bifurcations a threaded head portion 62 of the tielrod 19 and the pin 5S at the upper end portion 56 of the outer lever 12 is similarly secured at its opposite ends to the respective bifurcations of the lever 12 and rotatably carries another head portion 62 of the tie-rod 19. The head portions 62 are adjustably interconnected by a generally hexagonal bolt 63 having its opposite ends threaded and adjustably screwed into the respective head portions 62 and locked in an adjusted position by nuts 64.

The pin 55 atthe central portion of the inner shoe lever 11 is rotatably supported at spaced intermediate portions by the respective supports 211 which are bifurcated at their lower end portions 65 and fixedly secured to respective pins v66 Yrotatably carried by the re spective side members 41. The outermost end portions of the pin 55 are threaded and receive respective nuts 67.

The brake shoe 14 is fixed to the pin 55 and the brake shoe is rotatably supported on the pin 60. Each of the shoes has a friction lining 68 and, at the face opposite the lining, has a pair of laterally spaced anges 69 which have openings, respectively, receiving the associated ones of the pins 55 and 60. As is apparent, when the shoes 14 and 15 are` separated from the wheel 16, gravity tends to cause their upper ends to tilt toward the wheel. To prevent this tilting and thus to prevent the uppermost inner corners of the linings 68 from rubbing` on the wheel when the brake is 'released,.each of the shoes 14 and 15 is provided, at its lower end portion,

with an eccentric cam 70 adjustably positioned to engage a stop surface 71 defined by the upper edgeA of a plate 72 secured to one of the side members 41. Each vof the stop surfaces 71 is so shaped and positioned, and its associated cam 70 is so adjusted that, irrespective of the adjusted positions ofthe shoes. 14 and 15, the shoes will become concentric with the wheel 16 when the brake is released. Such anti-tilt means are described and claimed in a copending application of Arthur L. Ward, Serial No. 436,353, hled June 14, 1954, now Patent No. 2,871,994. It is. apparent that, other suitable anti-tilt means may be used if desired.

Prom the foregoing, it will be apparent that when the Y v lower end portion 52 of the inner shoe lever 11 is forced to the right, `as'viewed in Fig. l, the shoes 14 and v15 are forced against the wheel 16, and, when ,the lower end portion 52 is forced to the left, this shoe-applying force is relieved. For moving the shoes 14 and 15 away from the'wheelwhen all applying forces are relieved, a suitable return means is provided.y This Areturn means in Ythe form shown is a helical compression spring 74 interposed between an inner wall l5 of the base portion 44 and the inner end portion 61 ofthe thrust rod'24,. 1. The spring 74 forces the` lowerv endportion52of.thelever V11 to the left, and a helical compression spring '76, interposed between the magnety case 28 and the inner head 62 of the tie-bolt 19, forces the upper end portions 51 and 56 of the shoe levers 11 and 12 to the right.

An adjustable stop means 77 for insuring proper shoe clearance comprises a bolt 7S adjustably threaded into the armature plate 22 and 'loosely received in an opening 78 in a webportion 79 of the inner shoe lever 11 adjacent the end portion 51. A head portion Si) of the bolt 78 thus serves as an adjustable stop for determining the clearance between the shoes 14 and 15 and the wheel 16 when the brake is released.

Turning now to details of the operating magnet, the magnet housing 28 has a terminal box 31 on its upper surface provided with a removable top cover 82. Lugs 83 and 84 at opposite ends of the terminal box 81 extend outwardly from the respective end faces of the housing 28 and rotatably receive pins 85 and S6, respectively, secured at their outer end portions in upstanding spaced ear portions 87 of the respective armature plates 22 and 25. Cover-plates 8S and S9 enclose the respective coil receiving chambers 32 and 33. Leads 34a and 35a from the coils 34 and 35, respectively, enter the terminal box 81 for connection to a controller such as hereinafter described.' Preferably the coils 34 and 35 are so wound and connected to a power source that any ux produced by the winding 35 that might cross the air-gap between the outer pole 29 and the armature plate 22. is in the same direction as the flux across that air-gap produced by the winding 34. This prevents inadvertent release of the armature 22 upon strong energization of the winding 35.

The brake-applying spring 21 is ydisposed around a manual-release rod 90 between an inner spring retainer 91, slidable along the rod 90 and abutting a depending portion or extension 92 of the armature plate 22, and an outer spring retainer 94 formed on an inner end portion 95a of a two-part torque adjustment sleeve 95 surrounding the rod 90 and having an outer coaxial portion 95b, (Fig. 4), adjustably threaded throughan opening in the end wall 42. An inner end portion of the rod 90 is loosely received in a recess 97 in the depend ing portion 92 and is threaded into a bore 98 formed in the push rod 24. The length ofthe spring 21, and thus the spring-derived torque of the brake, can be adjusted by turning the sleeve portion 95b in the end wall 42, and the sleeve portion 9517 can be locked in adjusted position by a nut 99. A nut on a threaded outer end portion 101 ofthe rod'90 can be turned to compress the spring 21 and thereby eiect manual release of the brake. l 1 Outer end portions of theV bars 26 are received on respective pins 104 rotatablysecured to respective bifurcated end portions ofV a pairof lugs 105 vwhich depend from the armature plate 2,5.

' From the foregoing description, it will be seen that energization of the .coil 34 causes clockwise rotation of the armature plate 22 as viewed in Pig. 1 and consequent compression of thebrake-applying spring 21. This relieves the forcevfromv the, lower end portion of the inner shoe lever 11.and the shoe leverll turns clockwiseunder the iniiuence of the springs 74 yand 76. The lever 11 pivots atthe pin 55 ,upon this .initial clockwise movement, forcing the lever 12 clockwise and moving the shoe 15 away'from the wheel 16'. When the web portion 78a strikes the stop head .80, pivotal movement can no longer occur at the pin 55 and the armsj20 rpivot counter;

, clockwise at the pin '66 to move the shoe 14 away from A, 52 of the lever 11 to theright.Y Ihis movement ofthe.

` lever 11. causes the supports 2,0 to turn clockwise to apply the Yshoe'14 to the wheel 16.. As soon as .the shoe 14 aovaae engages the wheel, the lever 11 turns counter-clockwise at the pin 55 and pulls the lever 12 in a counter-clockwise direction and causes the shoe 415 to engagethe Wheel 16. Y l

lf, while the coil 34 is energized, the coil -35 is energized, the armature plate 25 turns counter-clockwise, as viewed in Fig. 1, and forces the spaced rods 26 to the right.A This moves the lower end portion 52 of the inner shoe lever t11 to the right and applies the shoes14 and 15 to vthe Wheel 16 with a force proportionalto the amount of pull on the armature platel 25. n From the foregoing, it isseen that as the linings 68 wear, it is necessary to adjust the bolt 78 of the adjustment means 77 to insure proper clearance of the shoe 14 and to.V adjust the length of the tie-rody 19 to equalize the shoe clearance. e

A wiring diagram of a suitable control systemA for controlling the energization ofthe coils 34 and 35 y,is shown in Fig. 5. Referring to Fig. 5, a brakepedal 110 suitably pivoted at 111 is arranged to be moved downwardly against-the force of a spring 112. Initial downward movement of the pedal 110 closes spring-biased contacts 114 to complete a circuit from a conductor 115 constituting one side of 'a Vsuitable source of direct-current through the coil 34 to the other side of the'source represented by the conductor 116. Thus initial movement of the pedal 110 causes energization of the coil 34 and release of the brake. Subsequent movement of the pedal 110 in the down direction causes closure of springbiased contacts 118 which complete a circuit from the conductor 115 through a suitable rheostat 119, shown as of the carbon-pile type, and the coil 35 to the negative conductor 116. The coil 35 is thus initially energized at a low value determined by the'uncompressed resistance of the rheostat 119, and causes the shoes 14 and 15 to engage the wheel 16 and exert a low braking force.

I Further downward movement of the pedal 110 compresses the carbon discs of the rheostat 119 reducing the resistance ,and accordingly increasing the energization of the coil 35. Increased energization of the coil 3'5 causes the armature plate 25 to exert increased force on the lever 11. Thus the degree of brake application can be.

controlled by the extent of depression of the pedal 110. Release of the brake is accomplished by relieving pressure on the brake pedal 110, permitting the spring 112 to Aforce the pedal upwardly and open the `contacts 118 and 114'- Should power fail at any time, the coil 34' becomes deenergized and the spring-21 immediately applies the brake with the maximum adjusted force.

It is apparent that other suitablesystems can be used to energize the coil 34 and then to energize and increase and decrease theenergization of the coil 3,5. For example, a modiiied system is shown in Fig. 6. Here a brake pedal 130, suitably pivoted at 131, is arranged'to move downwardly against the force of a'spring 132.`

Initial downward movement of the pedal 130 'closes spring-biased contacts 134 to complete an obvious circuit position, force exerting means urging said brake *apply*- ing means towards saidbrake applying position,s ec ond motive means electrically energizable to restrain said forcevr exerting means, support means supporting said first and second motive means4 in a flux conductive relationshipin which at least someY of the flux from one of said motive means may thread the othery of said motive means, and a Yflux conductive means carried bythe support means and interposed between said rst and second motive means to shunt the flux from one motivemeans away from the other motivemeans. Y

2. A brake comprising brake means having a brake applying .operation and a brakereleasing operation, iirst electromotive means coupled toV said brake means and electrically energizable -to eifect -said brake applying operation of said brake means only while said first'electromotive meansk is electrically energized, force exerting means coupled to said brake means and urging said brake applying Aoperation ofsaid brake means, second electromotivel means operatively associated with said force exerting means andelectrically energizable to restrain the urging of said force exerting means only while said second electromotive means-is electrically'energized, supporting" means supporting one of said electromotive 'mansin the ii'eld of magnetic lflux oftleother lofy said electromotive means, and a magnetic shunt shunting said for the coils 34 and 35.` Energization of the coil 34 de- Y activates the spring, but concurrent energization of theV coil 35 keeps the shoes applied to the wheel. As the pedal is moved further in the downdirection, a rheostat arm 135, pivoted at 136, moves to insertmore and more of a resistor 138 in series with the coil 35, causing its energization to v diminish and reduce the braking torque. Finally, the pull of the coil'35 becomes small enough to permit ythe shoes -14 and 15 jto separate vfrom l the wheel.'` Release of the pedal 130 causes'brrakinrgtorque to be applied in an increasingl amount until'the contacts' 134 open to deenergize the coilj34, thereby permitting the spring.21 to set the brake,v y,

VHaving thus described-my invention, I claim: n' l movable towards and away from Vbrake' -applying posi- .I

. one of said electromotive'means to limit the number of magnetic lines of ux passing from said other of said electromotive means through said one of said electromotive means. v

3. A brake comprising brake means having a brake applying operation land a brake releasing operation, firstV electromotive means coupled to said brake'means and electrically energizable to eiect said brake applying operation of said brakemeans only while said first electromotive means is electrically energized, force exerting means coupled to said brake means and urging saidbrake applying operation` of said brake means, second electromotive means operatively associated with s'aid force exerting means and electrically energizable to restrain the urging of said force exerting means only while said second electromotive means is electrically energized, 'supporting means supporting one of said electromotive meansin the lieldof magnetic flux of the other of said electromotive means, and a single shunt. simultaneously and magnetically shunting both of said electromotive means to limit the number of magnetic lines of ilux passing from either electromotivey means through the other electromotive means. n

4. A braking device comprising brake applying means movable towards and yaway from brake applying position,'rst electromagnetic means electrically energizable t to move said brake applying meansl towards said brake applying position, force exerting means urging said brake applying means towards said brake applying position, second electromagnetic means electrically energizable to restrain said force exerting means, each of said electromagnetic means including a llux path defined by stationary flux conductivemeans and .movable ilux conductive means movable relative to the stationary flux y conductive means to provide an air gap in the said ilux path, and shunt means common to both flux paths and 'l forming a flux conductive shunt for each flux path around the airv gap in the other flux path.

' 5. Thestructure of claim-t wherein'the means supported'by the framefand comprising a unitary' 1. A braking device 'comprising brake applying means i generally Cylindlal Shape-d .bOdY fully CIlta/illillg'ra Pair of operating coilsdisp'osed in coaxial relationship toj one another' and to the body, brake applyingrbar means'at Y u' oneside ofthe body, a pair off armatures 'pivoted at the e stationary lilux Vconductive'meansof the iirst and second electromagnetic means vare interjoined with said shunt means and extendy outwardly; in respective opposite directions from said other side of the body, each by one of its ends, fo1 swingeach being responsive to the coil adjacent to it so that upon energization of either coil the varmature adjacent to it is swung toward the body, and, upon deenergization of either coil, the armature adjacent to it is released for movement away from the body, said free end portion of said armatures operatively engaging said bar means for moving said bar means linearly toward a .braking position when said one armature swings in a direction toward the body, return means for returning the bar means and the free end portion of said one armature in the opposite direction, said mounting frame including a pair of spaced apart side walls extending endwise of the body audrdisposed entirely at said one side of said body and containing said brake applying bar means, -said return means, said free endk portions of said movable armatures, a manual release rod and brake applying .compression spring, said bar means being operable whenimoved toward said braking position to move a,y pair of braking shoes .to braking position, said brake-applying spring be` ing disposed in generally parallel spaced relation to said release rod and concentric therewith and operative normally to urge said shoes to braking position and comfrs pressible to release said shoes for return movement of said shoes out of braking position, and said free end portion of the other of ,said armatures operatively engaging said spring so that when said other armature swings in a vdirection toward the body about-its pivot the spring is `compressed and, when said other armature swings in the opposite direction, the spring urges said shoes to braking position.

7. The structure according to claim 6 wherein said body means hasy flux lconducting means simultaneously dening a magnetic path for the flux produced by any one of'said flux Vproducing means', and a magnetic shunt path shunting thek remaining of said i'luX producing means.

ReferencesCited in the file of this patent Y UNITED sTATEs PATENTS 837,400 Grosvenor Dec. 4, 1906 2,065,259 Ball et a1. Dec. 22, 1936 2,515,468 Piron July 18, 1950 2,792,080 Dunlop May 14, 1957 FOREIGN' PATENTS Y 1,073,063 f VFrance Mar. 17, 1954 Y 138,092 Switzerland Apr.lv 16, 1930 

